Oliver has displaced Jack as the nation's most popular boy's name, while Olivia remains in top spot on the girls' list. Photograph: Flying Colours/Getty Images

Olivia and Oliver have joined hands to take the top two places in Britain's annual ranking of new babies' names, with Jack tumbling down after holding the boys' crown for 14 years.

But in keeping with national politics, parents have shown a strongly conservative tendency overall, with no new entries in either gender's top 10, just a reshuffling of the order.

Spelling variations have also kept Mohammed in 16th place, with Muhammed at 36 and Mohammad at 62. Combined, the total of 6,255 infants named after the prophet in 2009 would make the top five, just as joining Harry (3rd this year) with Henry (37th) would knock Oliver into second place.

Relative newcomers among the 706,248 births are making progress further down the rankings, produced by the Office of National Statistics (ONS) to lighten its usual sober fare of figures on health, employment and population. The girls' top 100 includes both spellings of Madison, which comes 59th while Maddison is 68th.

Summer easily beats both at 24th, and Skye is 71st, although its alternative version, Sky, fails to qualify. Change is more evident in the regions than nationally, with Isabella going straight to sixth place in London and Lucy and Ava making their debut in the North East. Mohammed tops the boys' list in the West Midlands, unaided by other spellings.

Researchers with time on their hands will also be able to show a national determination not to be bound by convention, in spite of the popularity of a small number of names. Registrars recorded no fewer than 34,100 different names for girls and 26,800 for boys during the course of the year.

Despite losing the national title, Jacks can find consolation in Wales, the north-east and the north-west, where the name remains first choice for boys. Overall, the ONS archivists detect a revival of names which were last popular for babies born in the 1920s and early 30s; many such names later became synonymous with the feisty heroines of wartime Britain or the austerity period before the 50s.

Examples include Evie, Ruby and Lily, which have respectively jumped 157, 91 and 45 places among the girls, and Alfie and Charlie among the boys, which are respectively up 60 and 25 places on the figures for 2008. Britain's more liberal officialdom has given these names a hand; until the 1950s, parents were rarely allowed to register shortened or familiar versions of names.

Stayers in the lists are Jack, Joshua, Thomas, Daniel and William, which were all in the top 10 a decade ago, as were Olivia, Chloe, Emily, Sophie and Jessica among baby girls. William and Thomas were up there a century ago, too, but time has yet to bring a revival of other Edwardian favourites such as Edith and Ernest.

The ONS used the statistics to remind parents to include infants in the national census due in March. A spokeswoman said: "Babies often go unrecorded, as new parents don't always realise that they need to enter the details of even the very newest member of the household. It matters, because there is a strong link between filling in the census and the authorities being able to plan and provide public services in years to come.

The published figures do not highlight any infants landed with entire football or cricket teams' lists of names, let alone the poor child featured in a music hall song about the Boer war. Drowning in jingoistic propaganda, the parents tell the vicar in the chorus: "The baby's name is Kitchener, Carrington, Methuen, Kekewich, White, Cronje, Plumer, Powell, Majuba, Gatacre, Warren, Colenso, Kruger, Capetown, Mafekin, French, Kimberly, Ladysmith, 'Bobs', Union Jack and Fighting Mac, Lyddite, Pretoria Blobbs.